Types of Crime Scene Prints

Three Types: Patent Prints Plastic Prints Latent (Invisible) Prints

Patent Prints Can be seen with the naked eye Made by fingers touching a surface after ridges have been in contact with a colored material such as blood, paint, grease, ink, etc.

Plastic Prints Can be seen with the naked eye Made by ridge impressions left on a soft material such as putty, wax, soap, dust, wet painted surfaces, etc.

Latent (Invisible) Prints Latent fingerprints are those that are not visible to the naked eye. These prints consist of the natural secretions of human skin and require development for them to become visible. They are made by impressions caused by transfer of body perspiration or oils present on finger ridges to the surface of an object

Detection of Prints Latent prints must be developed (found) through different methods The method used is dependent on the surface being examined

Surface Conditions Hard, nonabsorbent surfaces (glass, mirrors, tile, painted wood): Powders or Super Glue Fuming Absorbent surfaces (paper, cardboard, cloth): One or more specific chemicals

Fingerprint Powders Non-absorbent surfaces only Applied with a camel’s hair or fiberglass brush (DO NOT TOUCH) Color of powder chosen contrasts with surface color Powder adheres to oils and perspiration left by ridges Print can be lifted off the surface and preserved

How to Develop Fingerprints With Black Powder

Fingerprint Powders Some investigators use fluorescent powder and UV lights to help them find latent prints on multi-colored or dark surfaces. Magnetic powder can also be used to reveal latent prints. This type of powder works better on shiny surfaces, some paper, or plastic baggies or containers.

Iodine Fuming Oldest chemical method for developing latent prints. Iodine is a solid crystal that, when heated, is transformed into a gas through sublimation

Iodine Fuming Iodine fumes react with oils and fats to produce a temporary yellow-brown colored print. Iodine prints are not permanent and must be photographed immediately or fixed with starch solution, which can last about 1 month

Ninhydrin Chemical used to develop prints on porous material by reacting with amino acids in perspiration Developed prints appear purple-blue in color Prints appear within an hour or two and fully developed in hours Commonly used on paper products

Superglue Fuming Used on nonporous surfaces such as metal, electrical tape, leather, and plastic bags Active ingredient: cyanoacrylate ester Evidence is placed in a fuming chamber and the cyanoacrylate is heated and covers the object and produces a hard white latent print

Super Glue Fuming

Laser Light Perspiration contains a variety of components that fluoresce when illuminated by laser light Because of the fluorescence, latent prints can be seen with the naked eye Almost never used anymore with the invention of alternate light source (ALS) latent print examination

Alternate Light Source (ALS) Works because perspiration fluoresces under different wavelengths of light Can adjust the wavelength of light to be aimed through a fiber optic cable More commercially available than laser light setups

Preservation of Prints Common fingerprint methods do not interfere with further DNA analysis However, when biological material remains, fingerprints should be developed at the crime lab instead of at a crime scene

Preservation of Prints After prints have been found, photos must be taken If object is small enough to be transported without destroying the print, it should be preserved intact Cellophane should cover the print to protect from damage

Preservation of Prints Prints on immovable objects should be lifted Lifted prints should be preserved on a card that provides contrast

Kendall/Hunt Publishing Company21 Palm - friction ridges can be identified and may be used against suspects Other Prints

Kendall/Hunt Publishing Company 22 Footprints are taken at birth as a means of identification of infants. Other Prints

Iris Scan recognition is the process of recognizing a person by analyzing the random pattern of the iris. The automated method of iris recognition is relatively young, existing in patent since only 1994.

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